Gain deviation, I/Q gain imbalance, I/Q quadrature deviation, and I/Q delay imbalance occur in a receiver of a communication system utilizing quadrature signals. Gain deviation is gain difference between an actual output signal and an ideal output signal caused by gain errors of gain modules in signal path. I/Q gain imbalance is gain difference between an I channel output signal and a Q channel output signal caused by inherent circuit level mismatches between circuits in the quadrature signal paths. I/Q quadrature deviation is an orthogonal degree of an I signal and a Q signal caused by local oscillator signal generation circuit and mixer circuit errors. I/Q delay imbalance is a delay difference between an I channel output signal and a Q channel output signal caused by inherent circuit level mismatches between circuits in the quadrature signal paths. I/Q quadrature deviation and I/Q delay imbalance both result in phase imbalance, and are combined as I/Q phase imbalance. I/Q quadrature deviation and I/Q delay imbalance can not be separated using traditional methods for measuring receiver parameters. But separation of I/Q quadrature deviation and I/Q delay imbalance is of great value to chip design, because if I/Q quadrature deviation and I/Q delay imbalance can be separated, it will be easier to determine chip design modifications i.e., whether to modify the mixer and local oscillator signal generation circuits if I/Q quadrature deviation is high, or to modify the I/Q paths if the I/Q delay imbalance is high, to improve receiver's performance.
In another aspect, outside generated testing signals and inside generated special testing signals (e.g. PN training signal is used to measure receiver parameters as described in the U.S. Pat. No. 7,130,359) are used to measure receiver parameters in traditional technologies. It is not convenient to test a chip with outside generated testing signals because a testing signal generating device and related circuit paths on test board are needed. To measure receiver parameters using inside generated special testing signals, the receiver must include a circuit for generating the signals. Such circuits are relatively complicated, therefore increasing the cost and area of the chip.
In another aspect, gain deviation is corrected by calibrating corresponding gain modules individually in traditional technologies. Unfortunately, this is a complex procedure, and the precision of the result may be not high enough. In addition, this calibration method requires calibration function built in each individual gain module.
Therefore, it is necessary to provide a new method for measuring and correcting receiver parameters to solve the problems mentioned above.